Qinghai means "blue lake", and indeed the name of the province comes from the pristine waters of the vast Qinghai Lake high on the plateau - the 'roof of the world.' Three great rivers rise in Qinghai: Yellow River and the Yangtze River nurtured dazzling Chinese civilizations that sprang up along their valleys; the Lancang River starts here too irrigating first Tibet and Yunnan, before flowing through Southeast Asia as the Mekong.